Your computer will collect a lot of junk as you use it. Everything that you do with your computer will leave a little trail you could say, or a marker. Even the Internet will leave these on your computer. If you let this build up, your computer will start to slow down.
One thing you can do to avoid this is to clean out your hard drive once and a while. The steps below will guide you through this process.
Click and open MY COMPUTER
Right Click the C Drive, which is your primary hard drive for your computer. And select Properties.
Than click the DISK CLEANUP tab
On this window, select options that are not important to you, or select all of them. And than click OK. Let the process run, you will get a conformation window asking if you really want to do this, click on OK or YES.
By doing this process, you are freeing up space on your hard drive and also getting rid of unwanted files that build up on your computer. It’s a good step to do every so often.
Another option you have to increase your computers speed or performance would be adjusting your performance options. The following steps below will guide you through this process.
Right click MY COMPUTER either on your desktop or under the start menu and select properties
On the window that came up, in the performance window click the SETTINGS TAB
On this window, you have options to change the way windows performs. Select which one's you feel best with, but if your looking to get better or faster performance out of your computer, select ADJUST FOR BEST PERFORMANCE. Than click OK. Also, scroll down the list and re-select the "Use drop shadows for Icons on the desktop" this way your desktop icons wont look funky.
By doing this, your screen will change, your computer will change the display image leaving you with the older windows version. You can change this back by doing the following steps.
Go to your control panel and select DISPLAY
Select the APPEARANCE tab. 
On this window you will have the option to change the color of windows.
Under the WINDOWS AND BUTTONS: select which you would like, (Windows classic style) or (Windows XP Style) which is want you probably want. Under that you will see the COLOR SCHEME, select that and change the color of your computer.
You only have 3 options, so select which one you like best. Than click ok and your done!